SEA TROUT— DESCRIBED. 169 



anticipated, mostly a very short lower limb to the preopercle. The general length 

 in the female young is about \ of the total length, but in males it may be, 

 but rarely is, even f . When the fish attains 12 or 14 iaches in length, the head 

 of the male is generally about 4| in that of the entire length of the fish, and of 

 the female •§•. In adults and breeding fish, consequent upon prominence of the 

 abdomen, the body is deeper than at other periods of the year, or among spent 

 fish. Eyes — situated as already described, their diameter varying with the age 

 and sex of the specimen. Interorbital space convex. During the breeding season, 

 a knob shows itself at the upper end of the lower jaw, diminishing in size subse- 

 quent to this period. The posterior extremity of the maxilla, reaches to below 

 the middle of the eye in the par of this form, and beyond its hind margin ia the 

 adults. It has been asserted that the strength of the maxillary and mandible* 

 is much greater in the sewin Salmo cambricus, than in the salmon-trout 8. trutta, 

 a conclusion not borne out when a large number of specimens are examined. The 

 form of the gill-covers has been already referred to, but it must be noticed in 

 these bones having a squamous articulation together, that the lower end of the 

 opercle more or less overlaps the upper portion of the subopercle, and this 

 may interfere with the measurements. f In some examples, the posterior or 

 vertical limb of the preopercle is sinuous, in others, more or less rounded : while 

 the lower limb of this bone may be short, J of moderate extent and even sinuous. 

 The posterior margin of the opercle and subopercle form a semicircle, of which 

 the lower bone generally, but not invariably, forms the most prominent portion. 

 Several raised and curved lines are mostly present near the outer part of the 

 opercle and subopercle, but which are more visible in dried than in fresh 

 specimens. Teeth — ^in both races of sea trout there exist teeth across the hind 

 margin of the head of the vomer, and also in a double line along the shaft of that 

 bone ; these teeth are lost with age, commencing on the shaft from behind, but 

 gradually extending forwards. While it seems to be a general rule that the 

 sewin loses them more rapidly than the salmon-trout. But there are so many 

 variations ih. this among the sea trout, that no criterion as to species can be 

 deduced from the number or position of the vomerine teeth. Fins — speaking 

 generally, the fins in the two races of sea trout appear to be somewhat of similar 

 ' length, except the caudal, which in sewin up to about 15 inches in length, are 

 mostly longer, and more deeply cleft than in the salmon-trout. The peotoral§ 

 in young fish is occasionally shorter than in adults, being from 8 to 9 in the total 

 length, whereas in specimens over 14 or 16 inches long, it is usually from *!\ to 8 

 in the same distance, while it becomes more rounded with age. The length of 

 the rays of the dorsal and anal fins varies considerably among these fishes, for 

 although they are mostly comparatively longest in the immature, this is not 

 invariably the rule. It has been asserted that the distance from the front edge of 



* Dr. Gunther suggested that when a doubt arises respecting a specimen, "only an 

 exammation of the internal parts of the maxillary and mandible can decide to what species such 

 individuals ought to be referred, these bones being much stronger and more solid in S. cambricus 

 than in S. trutta." 



t Some authors consider the form of the gill-covers to be affected by sex, others that the 

 modifications which are seen are of no specific value whatever. 



X Dr. Giinther, when re-naming the Sahno albus, also known as S. phinoc, Turton (which had 

 been long recognized as the grilse stage of the S. trutta), S. brachypoma, Giinther took as his 

 seven examples four skins from Parnell's collection, one of which had been figured on plate 32, 

 fig. 3, as a bull trout, three were marked S.fario, and one S. eriox ; one from Yarrell's ooUeotion, 

 and two specimens from the Ouse. The length of the head was given as 4| in that of the total 

 excluding the caudal fin, and 4 times in the males, but no mention was made if the specimen 

 measured was merely a dried skin. He gave the measurements of 5 sea trout, as follows : S. trutta, 

 male, 18J inches long, head 4J in the total excluding the caudal fin. S. cambricus, male, 

 Bhymney, 24 inches long, male, head 4^ ; a female 221 inches, head nearly 4 ; a male, 14 inches, 

 head 4J ; a male, 6J inches, head 4^. 



§ The following give the results of some of the measurements made : salmon-trout, male, 

 20 inches long, pectoral 74 in the total length, at 16-6 in. long 74, at 16-6 in. long 8, at 14-8 

 in. long 8, at 12-3 in. long 7i. Sewin, at 15 in. long 9f , at 13-3 in. long 8, at 13 in. long 9. 

 Salmon-trout, at 12-3 in. long 7}. Sewin, at 12-5 in. long 9, at 12-6 in. long 9. WMte-fish, 13-4 in. 

 long 8, at 12-4 in. long 8J. Whitling, at 9-5 in. long ^\, at 8'2 in. long 8. Traff, at 8-2 in. long 8, 

 WhitUng, at 8-1 in. long 8, at 7-8 in. long 7i, at 7-5 in. long 7|. 



